1. Technical Field
Embodiments of the present disclosure relate to semiconductor devices executing a refresh operation.
2. Related Art
A semiconductor device such as a dynamic random access memory (DRAM) device includes a plurality of memory cells for storing data. Each of DRAM cells is configured to include a cell capacitor and a cell transistor. The DRAM device stores data therein by discharging or charging the cell capacitors. Once the cell capacitor is charged or discharged to store a datum therein, an amount of electric charge stored in the cell capacitor is ideally constant over time. However, the amount of electric charge stored in the cell capacitor actually varies because of a voltage difference between the cell capacitor and a circuit adjacent to the cell capacitor or because of a leakage current of the cell capacitor. In particular, if the amount of electric charge stored in the cell capacitor is reduced, the cell capacitor may lose a datum stored therein, resulting in a malfunction of the DRAM device. Thus, the DRAM device may require a refresh operation to prevent the memory cells from losing their data.
As a semiconductor device becomes more highly integrated with the development of process technologies, a distance between memory cells as well as a distance between word lines connected to the memory cells has been continuously reduced. If the distance between the word lines is reduced, data stored in memory cells adjacent to a selected memory cell may be changed due to a coupling phenomenon or an interference phenomenon between the word lines.